Thin film composite (TFC) membranes are used in a variety of fluid separations. The thin film layer may be formed by an interfacial polycondensation reaction between polyfunctional amine (e.g. m-phenylenediamine) and polyfunctional acyl halide (e.g. trimesoyl chloride) monomers which are sequentially coated upon the support from immiscible solutions, see for example U.S. Pat. No. 4,277,344 to Cadotte. Various polyfunctional acyl halide monomers and combinations of monomers have been studied. For example, U.S. Pat. No. 4,259,183 to Cadotte describes combinations of bi- and tri-functional acyl halide monomers, e.g. isophthaloyl chloride or terephthaloyl chloride with trimesoyl chloride. Tetraacyl halide monomers are also described in the literature, see for example: i) Lei, Li et al., Polyamide Thin Film Composite Membranes Prepared from Isomeric Biphenyl Tetraacyl Chloride and m-Phenylenediamine, Journal of Membrane Science, 315 (2008), pg 20-27; ii) R. J. Peterson, Composite Reverse Osmosis and Nanofiltration Membranes, Journal of Membrane Science, 83 (1993), pp. 81-150 (see for example pg. 116-117) and U.S. Pat. No. 6,162,358 which both describe the use of adamantane-2,6 dione-1,3,5,7 tetra carbonyl chloride, and iii) CN 102219673 which describes the formation of nano filtration membranes using combinations of 5,5′-methylenediisophthaloyl dichloride, trimesoyl chloride and piperazine.
Membranes are commonly characterized in terms of their water and NaCl permeability coefficients, i.e. “A” and “B” values; see Mulder, Basic Principles of Membrane Technology, 2nd Ed., Kluwer Academic Publishers (1996). While reverse osmosis (RO) membranes commonly have B values for NaCl of less than 0.3 GFD, much lower values (e.g. less than 0.04 GFD) are desired in specialty applications.